A system to link a vehicle on-board unit with a mobile device is disclosed, for example, in Japanese Patent Application Laid-open Publication (JP-A) No. 2003-244343. The disclosed system includes an on-board unit of a vehicle and a mobile phone, which can be linked together such that when the user operates a changeover switch of the mobile phone, the mobile phone is connected to the on-board unit whereupon a screen of the mobile phone is switched to a non-display state.
The mobile device such as mobile phone can be used with various applications, however, for some sort of applications, execution is not desirable while the vehicle is moving or in motion.